The present invention relates to a novel chemical structure comprising rutile titanium dioxide (TiO2) nanoparticles, and, more particularly, to ordered acicular aggregates of elongated TiO2 crystallites which resemble nano-sized flower bouquets and/or triangular funnels.
Titanium dioxide (TiO2) is known as a typical solid compound having photocatalytic activity and having utility in electronic, photovoltaic and photonic applications. Rutile and anatase crystal forms are known as major crystal forms of TiO2 which display higher chemical stability and larger refractive indices than those of amorphous TiO2. It has also been recognized that TiO2 particles having a high degree of crystallinity can exhibit a desirable level of photocatalytic activity.
U.S. Patent Publication No. 2012/0132515, for example, describes rutile TiO2 nanoparticles wherein each has an exposed crystal face, making the nanoparticles useful as a photocatalyst and oxidation catalyst. The TiO2 nanoparticles are produced by subjecting a titanium compound to a hydrothermal treatment in an aqueous medium in the presence of a hydrophilic polymer, which is polyvinylpyrrolidone. The titanium compound, when hydrothermally treated in an aqueous medium, generally gives a rod-like crystal of rutile titanium dioxide having (110) and (111) faces. However, when hydrothermally treated in an aqueous medium in the presence of polyvinylpyrrolidone, the rod-like crystal which results exhibits a novel exposed crystal face (001). It is noted that the hydrophilic polymer acts as a steric stabilizer or capping agent to thereby prevent aggregation of the rod-like crystals of rutile titanium dioxide.
The need exists for improved methods for producing novel types of rutile titanium dioxide (TiO2) nanoparticles which have high surface areas, e.g., in the range of from 120 m2/g to 160 m2/g, and high refractive indices for improved UV blocking capability and which demonstrate high performance levels in catalysis, e.g., biomass conversion, and in electronic applications, such as lithium ion batteries and fuel cells.